[SNMP4J] ConcurrentModificationException on close()

[Paul Donohue]

I'm regularly seeing a java.util.ConcurrentModificationException when I call close() from my ResponseListener.  It appears to happen on occasion in all three of my calls to close() (after a timeout, after an error, and even after processing a valid response):

   ResponseListener listener = new ResponseListener() {
     public void onResponse(ResponseEvent event) {
       // Always cancel async request when response has been received
       // otherwise a memory leak is created! Not canceling a request
       // immediately can be useful when sending a request to a broadcast
       // address.
       ((Snmp)event.getSource()).cancel(event.getRequest(), this);
       if (event.getError() instanceof InterruptedException) {
         System.out.println("Interrupted: "+event.getError());
       } else if (event.getResponse() == null) {
         System.out.println("Timeout");
         ((Snmp)event.getSource()).close();
       } else if (event.getError() != null) {
         System.out.println("Error: "+event.getError());
         ((Snmp)event.getSource()).close();
       } else {
         System.out.println("Received response PDU is: "+event.getResponse());
         ((Snmp)event.getSource()).close();
       }
     }
   };

[...]
Timeout
java.util.ConcurrentModificationException
        at java.util.Hashtable$Enumerator.next(Hashtable.java:1031)
        at org.snmp4j.Snmp.close(Unknown Source)
[...]

I see 3 possibly related reports on this mailing list of similar problems, but I don't see any relevant replies to them:
http://lists.agentpp.org/pipermail/snmp4j/2006-February/001039.html
http://lists.agentpp.org/pipermail/snmp4j/2006-October/001722.html
http://lists.agentpp.org/pipermail/snmp4j/2007-July/002362.html

Any suggestions for correcting this?
Should I skip the cancel() call when there is an InterruptedException?  If so, are there any other situations where I should skip the cancel() call?

Let me know if I can provide any additional information.

Thanks!
-Paul